50 research outputs found
AMS 14C ages of Yamato achondritic meteorites
Terrestrial ^C ages of some Yamato achondrites and other meteorites, have been determined by accelerator mass spectrometry (AMS). Samples of meteorites previously studied for ^C are reported, as are new measurements on Yamato achondrites. Results on a number of meteorites from the Yamato-79 series shows longer terrestrial ages than expected for this site, where young ages predominate. A new ^C age on Y-74037 confirms the younger age for this diogenite similar to Y-74097,whereas Y-74010 is older (15kyr) and these two data suggest there may be more than one diogenite fall in the Yamato-74 group
Annual radiocarbon record indicates 16th century BCE date for the Thera eruption
The mid-second millennium BCE eruption of Thera (Santorini) offers a critically important marker horizon to synchronize archaeological chronologies of the Aegean, Egypt, and the Near East and to anchor paleoenvironmental records from ice cores, speleothems, and lake sediments. Precise and accurate dating for the event has been the subject of many decades of research. Using calendar-dated tree rings, we created an annual resolution radiocarbon time series 1700–1500 BCE to validate, improve, or more clearly define the limitations for radiocarbon calibration of materials from key eruption contexts. Results show an offset from the international radiocarbon calibration curve, which indicates a shift in the calibrated age range for Thera toward the 16th century BCE. This finding sheds new light on the long-running debate focused on a discrepancy between radiocarbon (late 17th–early 16th century BCE) and archaeological (mid 16th–early 15th century BCE) dating evidence for Thera
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Identification of potential methane source regions in Europe using δ13 CCH4 measurements and trajectory modeling
The methane emissions from the Hungarian Pannonian Basin are not well qualified, due to a lack of measurements of CH4 mole fraction and δ13CCH4 in the air. This study reports methane measurements in air samples from Hungary, placing them in the context of regional and global background data, to investigate the inputs to the methane burden in Central Europe. CH4 mole fraction and δ13CCH4 from the Hungarian tall tower station, Hegyhátsál, and additional data from Mace Head (Ireland) and Zeppelin (Svalbard) are used with back-trajectory modeling to identify central European source areas and their seasonal variation between the summer vegetation and winter heating periods.
Methane measurements in air masses sampled in the European interior, have significantly higher maxima and seasonal amplitudes than at the Mace Head and Zeppelin European background sites. The mean CH4 mole fraction value is about 80 ppb higher than the comparable marine background, and values above 2000 ppb were frequently observed between February 2013 and December 2015. The mean δ13CCH4 value -47.5±0.3 ‰ (2σ) was comparable to values at all three monitoring sites, but specific pollution events were detected at Hegyhátsál. Concentration weighted trajectory modeling, meteorological parameters, stable carbon isotopic composition (δ13CCH4), and Miller-Tans analysis show that the main factors influencing CH4 at the Hegyhátsál, apart from diurnal and seasonal changes in the Planetary Boundary Layer, are emissions from residential heating and industrial CH4 emissions during the winter
Bomb-produced radiocarbon in the shell of the chambered nautilus: rate of growth and age at maturity
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Editors' Note
Center for Mediterranean Archaeology and the Environment (CMATE) Special Issue, Joint publication of Radiocarbon and Tree-Ring Research, also cited as Editors' Note. (2014). Radiocarbon, 56(4), V-V.This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive. For more information about this peer-reviewed scholarly journal, please email the Editor of Tree-Ring Research at [email protected]
Mammoth Extinction and Radiation Dose: A Comment
Recently, an article was published in this journal, discussing evidence for a solar flare cause of faunal extinction during the Late Pleistocene. The article is based on the hypothesis that an increase in atmospheric radiocarbon concentration might have been produced by a giant solar proton event (SPE). This proposed SPE would deliver a lethal radiation dose of at least 3–6 Sv to the surface of the Earth, causing termination of the Pleistocene megafauna.